Kettles occur as the result of blocks of ice calving (falling off) the front of a receding glacier and then becoming partially or completely buried by glacial outwash.
The occurrence of these stranded ice masses is thought to be the result of gradual accumulation of outwash atop the irregular glacier terminus. The glacial terminus or snout is the end of a glacier at any given point in time.
Kettles may range in size from 5 m (15 feet) to 13 km (8 miles) in diameter and up to 45 m (135 feet) in depth. When filled with water they are called kettle lakes.
Most kettles are circular in shape because melting blocks of ice tend to become rounded; however, distorted or branching depressions may result from extremely irregular ice masses. The viewpoint (R2) overlooking Winniford Lake will give you some indication of how irregular and large those ice masses may be.
When the development of numerous kettle holes disrupts sandur surfaces, a series of ridges and mounds may be seen surrounding the kettles. These kettle hole ridges are deposits of loose rock fragments and gravel called “till”. On the far side of the lake, you can see a massive deposit of glacial till, left by the receding glacier, called a drumlin. Kettle holes can also form as the result of floods caused by the sudden drainage of an ice-dammed lake.
The kettle in which you are parked (or standing) is bisected by the township road. A portion of the outwash till is still visible as the large mound next to the kettle. If you were to dig down into the mound, you would find an accumulation of gravel and rounded rock of various sizes beneath the rich surface soil. As you look around the edges of the kettle, you will see a lower ridge structure that has been cultivated and softened by time. Gravel for the construction of the road may have come from the glacial till of the kettle's surrounding ridge. There is a secondary kettle on the other side of the trees toward the south and others at viewpoint R1.
The development of distinct types of ridges depends on the concentration of rock fragments contained in the melted ice block and on how deeply the block was buried by sediment. Most kettle holes are less than two kilometres in diameter. However, Puslinch Lake in Ontario, Canada, is the largest kettle lake in Canada spanning 160 hectares (400 acres). The average depth of kettles is less than ten meters.
In most cases, kettle holes eventually fill with water, sediment, and/or vegetation. If the kettle is fed by surface or underground rivers or streams, it becomes a kettle lake. If the kettle receives its water from precipitation, the groundwater table, or a combination of the two, and is vegetated, it is called a kettle pond or kettle wetland,. Kettle ponds that are not affected by the groundwater table will usually become dry during the warm summer months, in which case they are deemed ephemeral or temporary.
If water in a kettle becomes acidic due to decomposing organic plant matter, it may become a kettle bog; or, if underlying soils are lime-based which results in neutralizing the acidic conditions, it becomes a kettle peatland. Kettle bogs are closed ecosystems because they have no water source other than precipitation. Both acidic kettle bogs and fresh water kettles are important ecological niches for many species of flora and fauna.
In order to log this cache, please email the cache owner the answers to the following questions:
(Please do not post your answers on the cache page. Cachers who have not sent their answers to the CO will have their logs removed.)
1) Based upon your observation of the average height of the ridge around the kettle in which you are standing, estimate the size (L x W x H) of the icy mass which was covered by the glacial outwash that formed this geological feature.
2) What clues in the area would indicate to you the glacier’s direction of movement and in which direction would the glacier have retreated?
3) Optional: Post a photo of the kettle(s) at the earthcache co-ordinates or from either of the viewpoints so that any change in the kettles may be observed over the years that this earthcache exists.